In many fields of electronics, in particular in entertainment electronics and automotive electronics, optical assemblies having at least one lens are being used to an increasing extent. The lens is part of a camera module, for example, for receiving and further processing optical stationary images or moving images. Such camera modules are used in cell phones (smartphones), laptops and tablet computers, for example. Such camera modules are also used in automotive electronics, for example, to record images of the road surface or to enable occupants of the vehicle to conduct video calls or to make photographs of themselves (selfies) or of the surroundings.
Such optical assemblies typically include a transparent front cover, behind which is arranged the lens which is separated from the front cover by an air gap. Light falling through the front cover is reflected partially at the front cover-air interface and also at the air-lens interface. The unreflected portion of light passes through the lens and into the camera module, which includes the lens, for example. An optical sensor (e.g., a CCD sensor or a CMOS sensor) in the camera module then converts the light striking the sensor into electric signals. This requires (expensive) camera modules, which are designed to compensate for the loss of light due to the light reflection.
The front cover often forms a light inlet opening of an otherwise opaque surface. This opaque surface may be, for example, the frame of a display device of a cell phone, of a laptop computer or of a tablet computer. In order for light to be able to strike the lens and a camera module through the lens, an aperture (often circular or square) is provided in the opaque surface, but this has a negative effect on the visual appearance of the frame, which is otherwise visually homogeneous.